1. Weather (you like it or not!)
Regent’s Earth Science - Topics #7

2. Weather Short term condition of atmosphere.
Due to unequal heating of Earth’s surface.
Happens in the troposphere (lowest atmosphere layer), because this is the only layer with water.
See pg #13
E.S.R.T.

3. All of these change when insolation changes.
Atmosphere Variables
Temperature
Dew Point
Air Pressure
Precipitation
Clouds
Wind
All of these change when insolation changes.

4. Heating of the Atmosphere
Conduction
Direct Absorption of EM insolation.
Absorption of Infrared from re-radiation by CO2 & H2O vapor.
Latent Heat released during condensation that makes clouds.
Frictional Drag as air rubs across Earth’s surface.

5. Heat Transfer in the Atmosphere
Transfer is by Convection.
Vertical - Warm Rises/Cool Sinks.
Horizontal - Pressure differences cause wind (the bottom ½ of convection cycle).
Air Cooling
Because it is far above Earth’s surface
Cool Air Sinking
Wind
Warm Air Rising

6. Adiabatic Heating & Cooling
(Orographic Effect)
Warm air forced up mtn. rises, expands & cools. So… windward side of mtn. ranges have precipitation.
Air dried before passing over mtn. range
Cool dry air forced to sink, compress & warm even more than it cooled due to lack of moisture. So… leeward side of mtn. ranges have deserts.
Vegetation thrives on windward side.
ie. Redwood Nat. Park
Mohave
& Moab Deserts are examples
Rain Shadow
Desert

7. Density & Atmospheric Pressure
Barometric Pressure IS Air Pressure!
Denser (cooler air) is HIGH pressure.
The weight of the stack of air atoms
above your head = air pressure.
Usually mb sea-level.
Mercury Barometer
Aneroid Barometer

8. Temperature & Pressure
As temperature increases Air EXPANDS & becomes less dense Lower Pressure

9. Moisture & Pressure
H (hydrogen) is the lightest of all elements. Increase H2O vapor Air is mostly N (nitrogen) & gets replaced by lighter hydrogen atoms SO… Air gets lighter w/ water vapor & Lower Pressure
Remember: HIGH DRY LOW WET

10. As altitude increases Less air over your head Lower Pressure
Altitude & Pressure
As altitude increases Less air over your head Lower Pressure

11. Wind Wind is a vector quantity.
Wind is named by the direction it comes from and measured w/ weather vane or wind sock.
Moves from high pressure to low pressure.
Wind is deflected to right in northern hemisphere by coriolis effect.
Clockwise & out from High pressure center
Counter-clockwise & in to a low pressure center

12. Wind Speed Fast Wind Slow Wind
The greater the pressure gradient the faster the wind.
Isobars closer means faster wind.
Measured w/ Anemometer.
Fast Wind
Slow Wind

13. Wind belts cause prevailing winds
Planetary Wind Belts
Wind belts cause prevailing winds
You are HERE!
SW Winds move NE
So our weather moves to the Northeast!

14. Surface Ocean Currents
They are pushed by prevailing winds.
So... Oceans circulate clockwise in the northern hemisphere & counter-clockwise in the southern hemisphere.
30° N
Equator
See ESRT
Pg #4

15. Atmosphere Moisture (Humidity)
Can be SOLID, LIQUID or GAS
Precipitation removes particles from air.
Aerosols become condensation nuclei
& then part of raindrops or snowflakes.
So precipitation cleans pollution from air.

16. Evapotranspiration Evaporation + Transpiration = Evapotranspiration
Evaporation is liquid to gas phase change.
Transpiration is water from plants

17. Evaporation Increases If…
surface area increases.
wind increases.
temperature increases.
relative humidity decreases.

18. Relative Humidity
Compares the amount of moisture in the air to what the air could hold if saturated at that temperature.
0% = None 50% = ½ full % = Saturated
(Full)
Warmer air atoms are farther apart so there is more space for H2O.

19. Dew Point Temperature is the Temperature Where…
air becomes saturated.
air reaches 100% relative humidity.
water vapor condenses into liquid water.
clouds form.

20. Dew Point Temperature & Relative Humidity ESRT References
Top of both tables is the difference between wet & dry bulb temps. Use that column.
Dry bulb IS the current air temperature. Use that row.
Sling psychrometer measures wet & dry bulb temps..

21. Dew Point Temperature & Relative Humidity ESRT References
10°C – 6°C = 4°C
Dry Bulb = 10°C
Wet Bulb = 6°C

22. Cloud Formation H2O in the air. Cool air to dew point temperature.
Condensation nuclei (dust particles) in air.
Warm air rises to the altitude of the DPT where the vapor condenses into billions of small cloud droplets.
Water vapor condenses
Altitude of Dew Pt. Temp.

23. Precipitation Tiny cloud droplets collide and stick together.
When droplets get large enough they fall through the rising warm air.

24. c = continental (dry) m = maritime (moist) P = Polar (cool) T = Tropical (warm) A = Arctic
Air Masses mP cP mP mT mT mT cT
maritime tropical

25. Hail particles circulate, freeze and grow in layers to get bigger.
Cold Front
Cold air push warm air
Cumulonimbus clouds
Thunderstorms
Lightning
Heavy Rain
Hail
Tornadoes . . 3
0°C .
Cold Air
(High Pressure)
Sinking
Hail particles circulate, freeze and grow in layers to get bigger.
Warm Air
Rising
Earth Surface

26. Warm Front (The Blue Line) Stratus clouds Overcast All-day rain
Warm Air
Rising
Cold Air
(High Pressure)
Earth Surface

27. Low Pressure System W/ Cold & Warm Fronts on Maps
Cool w/ Clear Skies
Overcast Skies
All-Day Rain H H
Cold Cold
Air Air
Warm
Air L
Possible Thunderstorms
Partly Cloudy
Nice
All of this will move to the NORTHEAST!

28. . Occluded Front Cold front catches up to warm front.
Stratus & cumulonimbus
All-day rain w/ thunderstorm at end
(Blue Lines) .
Warm Air
(Forced Up)
Cold Air
(High Pressure)
Cold Air
(High Pressure)
Earth Surface

29. Occluded Front on Maps
Cold dense air can move faster than the warm air.
So cold fronts catch up to warm fronts while rotating counter-clockwise.

30. Station Models NO UNITS on station model data.
See ESRT for data placement
Air Pressure Code
Drop Decimal Pt
Drop the 9 or
Un-coding Pressure
Put in Decimal Pt
Put 9 or 10 back so that # is between 950 &1050mb __